Summary: This paper provides an overview of the latest development in modeling and simulation of volume transition behaviors of hydrogels with models at both macroscopic and molecular levels. Energy conservation law, mass conservation law and momentum conservation law provide good starting points for developing models for hydrogel volume transition. Thermodynamic models, transport models, multiphasic mixture theory and molecular simulation are discussed. Thermodynamic models provide qualitative description of equilibrium volume transition of hydrogels. Both transport models and multiphasic mixture theory can predict transient and equilibrium volume transition of hydrogels. Molecular simulation provides mechanistic understanding of hydrogel volume transition. Several key parameters are summarized for future model development.